High Frequency Spectrum Efficiency Optical Transmission And Encryption System Performance Analysis

Whit the development of communication services, the requirements of access bandwidth and capacity in communication is also increasing, optical communication network has become an important part of a new generation of trusted network structure.Ro F(Radio-over-fiber) as a critical technology of broadband access system plays an important role in the implement of G-bps wired/wireless business. CO-OFDM and Nyquist-WDM technology can improve the spectrum utilization and realize high speed transmission in long distance simultaneously.On the other hand, in exploring the way to improve the transmission rate, spectral efficiency,capacity simultaneously in optical fiber transmission system, the security issues of high-speed optical communication systems also are arose spontaneously, becoming a hot topic of concern in the field of communications. A number of problems such as the Ro F transmission system performance, the CO-OFDM transmission system performance, the performance of Nyquist-WDM transmission system, chaos in DD-OOFDM and the application of 60 GHz Ro F-OFDM are studied in this paper. It has important theoretical significance and application value for the development of future high-speed communication network. In this paper, the main results obtained are as follows:1)Put forward 16QAM-OFDM full duplex WDM-ROF-PON wavelength division multiplexing passive optical network architecture. Downlink signal is 10 Gbps 16-QAM OFDM 60 GHz optical millimeter wave based on intensity modulation, central station in wireless and wired way to restore the original baseband signal,and utilize wavelength reusing technology to transmit OFDM uplink data.In the Ro F millimeter/THz communications systems radiation millimeter/THz waves, we have mastered Ro F millimeter wave/THz technology such as the frequency doubling technology, dual laser beat frequency method, dual wavelength laser beat frequency method. Successful experiments in 100 GHz band to achieve a 6Gb / s, over 5 meters distance wireless full-duplex Ro F.2)Propose a signal modulation format suitable for intensity modulation direct detection(IM/DD) optical systems.The subcarrier modulation(SCM) signal based on Nyquist pulse half cycle can effectively improve the spectrum efficiency, and compares the performance of PAPR in the CO-OFDM signal and SCM-Nyquist signal of the system. Packet encryption method and combined with linear encryption methods for channel decoding and high-dimensional chaotic encryption are proposed, used in CO-OFDM and Nyquist-WDM communication systems.3)Research and experimental verification that the OFDM signal transmission performance based on low density parity check code(LDPC) and Logistic chaotic encryption technology are increased in 60 GHz ROF system and the realization of system encryption. With the irregular length LDPC error correction code is used to reduce the dispersion effect in optical fiber link, utilizing Logistic sequence sensitivity of initial conditions as the key, can realize the encrypted transmission of data in the physical layer of OFDM-ROF system. 2.5Gb/s 64-QAM data transmission 30 km standard single-mode fiber(SSMF) in the downlink, when the bit error rate(BER) of 310-, LDPC coding improves the receiver sensitivity of at least 10 d B. No Logistic key for demodulation to bit error constellation, verify its encryption and strong error correcting ability and anti dispersion.